Grosjean believes go-karting is more challenging than F1

Romain Grosjean believes that go-karting is nowadays more physically challenging than competing in Formula 1.

The fallout continues after Lewis Hamilton said last week in the FIA press conference before the Canadian Grand Prix last weekend that Formula 1 used to be "a man's sport" and it is not as difficult as it used to be.

Grosjean, who has been in Formula 1 for 10 years, and has scored 10 podiums in that time, agrees with the five-time world champion: "Recently, I did a go-kart race with friends. 125cc with gearshift. And I was more tired than after a grand prix," the Frenchman said to Ekstra Bladet newspaper.

"Why? Because you are pushing all the time. But in F1, we are saving fuel and also the tyres. In Barcelona, it felt like we were driving at 50% of the car's capacity. If the race was like qualifying then our necks would be totally gone in the end.

"We would be tired and our focus would disappear. But constantly saving petrol and tyres means it is not difficult for us. Also, going back to refuelling would mean we don't have to run around with 100kg at the start but only 30-40kg. Then we would be a few seconds faster, if not more, and it would be harder."